Abstract

On the basis of transport theories appropriate to a radially expanding solar wind, new results for the radial evolution of the energy density in solar wind
fluctuations at MHD scales are derived. The models, which represent a departure from the well-known WKB description, include the effects of “mixing”, driving by stream-stream interactions and interstellar pick-up ion generated waves as well as non-isotropic MHD
turbulence.